Go on, in the name of God and in the power of His might...

I recently came across this in John Wesley's last letter - which he wrote to William Wilberforce:

"Unless God has raised you up for this very thing, you will be worn out by the opposition of men and devils. But if God be fore you, who can be against you? Are all of them together stronger than God? O be not weary of well doing! Go on, in the name of God and in the power of his might, till even American slavery (the vilest that ever saw the sun) shall vanish away before it."